Conventional window and door manufacture utilize structural members made commonly from hard and soft wood members and metal components, typically aluminum. Residential windows and doors are often manufactured from a number of specially shaped milled wood products that are assembled with glass sheets to form typically double hung or casement windows and sliding or hinged door units. Wood windows and doors while structurally sound and well adapted for use in many residential installations, require painting and other routine maintenance and can have problems under certain circumstances caused by the insect attack and by other deterioration of wood components. Wooden windows also suffer from cost problems related to the availability of suitable wood for construction. Clear wood and related wood products are slowly becoming scarce and costs increase rapidly as demand increases.
Metal windows and doors have been introduced into the marketplace. Such metal windows and doors are often made from extruded aluminum parts that when combined with rubber and thermoplastic curable sealant form utility components. Metal windows typically suffer from the drawback that they tend to be energy inefficient and tend to transfer substantial quantities of heat from a heated exterior to a cold environment.
Extruded thermoplastic materials have been used in the manufacture of window and door components. Typically, seals, edging, grill and coatings have been manufactured from filled and unfilled thermoplastic materials. Further, thermoplastic polyvinyl chloride materials have been combined with wooden structural members in the manufacturing of PERMASHIELD.RTM. brand windows manufactured by Andersen Corporation for many years. The technology for forming the PERMASHIELD.RTM. windows is disclosed in Zanini, U.S. Pat. Nos. 2,926,729 and 3,432,883. In the manufacture of the PERMASHIELD.RTM. brand windows, a polyvinyl chloride envelope or coating is extruded around the wooden member as it passes through an extrusion dye. Such coated members are commonly used as structural components in forming the window frame or double hung or casement units.
Polyvinyl chloride thermoplastic materials have also been combined with wood products to make extruded materials. Prior efforts have failed to manufacture a material that can be directly extruded to form a structural member that is a direct replacement for wooden members. Such prior art composite members fail to have sufficient modulus (typically about 500,000 or greater), compressive strength, coefficient of thermal expansion, coefficient of elasticity, resistance to insect attack and rot or deterioration, combined with ease of working and fastener retention to be a direct wood replacement material. Further, many prior art extruded composites require postextrusion milling to obtain a final useful shape. One class of composite, a polyvinyl chloride wood flour material, poses the added problem that wood dust tends to be explosive, as well as the need to size the wood particle, at certain concentrations of wood, dust or flour in the air.
Accordingly, a substantial need exists for the development of a composite material that can be directly formed by extrusion into shapes that are direct substitutes for the equivalent or corresponding shape in a wood structural member. The need requires a modulus (stiffness), an acceptable coefficient of thermal expansion and an easily formable material that can maintain reproducible stable dimensions, a material having low thermal transmission, improved resistance to insect attack and rot while in use and a material that can be cut, milled, drilled and fastened at least as well as wooden members.
A further need had existed in the art for many years with respect to the byproduct streams produced during the conventional manufacture of wooden windows and doors. Such window and door manufacturers have become significantly sensitive to the production of byproduct streams comprising substantial quantities of wood trim pieces, sawdust, wood milling by-products; recycled thermoplastic including recycled polyvinyl chloride and other byproduct streams. Commonly, these materials are burned for their heat value and electrical power generation or are shipped to qualified landfills for disposable. Such byproduct streams are contaminated with substantial proportions of hot melt and solvent-based adhesives, thermoplastic materials such a polyvinyl chloride, paint preservatives and other organic materials. A substantial need exists to find a productive, environmentally compatible use for such byproduct streams to avoid returning the material into the environment in an environmentally harmful way.